It's neat to look at the source material for this series. It was loosely based on A Little Princess by Frances Hodgson Burnett. It's pretty funny which characters are changed and what roles they play.

-Note that "Werec" is an anagram of "Crewe", Sarah's family name in the book.
-Becky the nurse is a bullied, overworked (and probably incompetent) scullery maid in the book.
-Lottie has tantrums in the book as well, and also seeks Sara's friendship. She is younger than Sara is in the book, consistent with her loli appearance in the series.
-Emily is still Sara's doll, and her most treasured possession.
-Melchisidec "Melchie" the chibi-genius, is a rat who lives in the wall in the book. Alternatively, Sara trains him, rather than the other way around.
-Lavinia is evil in the book, hates Sara, but still does pranks on her.

More details here:
Wiki: A Little Princess


I'm just glad this series paid attention to Relativity.